The present invention relates to a method for regulating the release of transforming growth factor xcex2 (beta), commonly known as xe2x80x9cTGF-xcex2xe2x80x9d. More particularly, the invention relates to the use of TGF-xcex2 regulators to prevent and/or treat neural tissue damage resulting from ischemia and reperfusion injury, neurological disorders and other neurodegenerative diseases; to prevent or treat vascular stroke; or to treat or prevent other disorders such as arthritis, diabetes, inflammatory disorders, disorders of the immune system, and cancer.
Transforming growth factor xcex2 (xe2x80x9cTGF-xcex2xe2x80x9d) is recognized as a prototype of multifunctional growth factors. TGF-xcex2 regulates a variety of important cell and tissue functions, such as cell growth and differentiation, angiogenesis, immune function, extracellular matrix production, cell chemotaxis, apoptosis and hematopoiesis. Members of the TGF-xcex2 superfamily are widely distributed with most adult and embryonic tissues expressing at least one member of the family.
Active TGF-xcex2 is a disulfide-linked homodimer consisting of two chains of 112 amino acids. Following interchain disulfide bonding between two pro-TGF-xcex2 peptides, proteolytic processing at a tetrabasic site cleaves the mature TGF-xcex2 domain from the amino terminal portion of pro-TGF-xcex2, which is called the latency associated protein (LAP). However, the mature TGF-xcex2 remains non-covalently associated with LAP, and this is the latent form of TGF-xcex2 that is secreted by most cells in vitro. The latent complex does not bind to the TGF-xcex2 receptor and so does not elicit a biological response. In vitro treatment of the latent complex with acid, alkali, chaotropic agents or heat releases biologically active TGF-xcex2, but the in vivo mechanism of activation is not entirely clear. Since many cell types express both TGF-xcex2 and its receptor, however, the activation of latent TGF-xcex2 is thought to be a critical control point in regulating the diverse biological actions of TGF-xcex2.
Biological actions of TGF-xcex2 are mediated through its binding to a heteromeric transmembrane receptor complex of two subunits designated type I (RI) and type II (RII), which are approximately 55 and 80 kDa, respectively. The current model of TGF-xcex2 ligand-receptor interaction proposes that RII, but not RI, can bind TGF-xcex2. Binding of TGF-xcex2 to RII induces the assembly of a heterodimer of RII-RI, transphosphorylation of RI by RII, and then activation of signal transduction pathways to elicit a biological response. About six type II and four type I mammalian receptors have been cloned, and they demonstrate different specificities and affinities for binding to different members of the TGF-xcex2 superfamily.
It has recently been demonstrated that disruption of the TGF-xcex2 signaling pathway can be involved in the pathogenesis of human cancers. TGF-xcex2 is known to suppress the growth of epithelial cells, and a disruption of this pathway can lead to uncontrolled proliferation. Disruption at any point in the TGF-xcex2 signaling pathway can contribute to the loss of tumor suppressor activity. In the nervous system, it is thought that a loss of neuroprotective actions of TGF-xcex2 may result from mutations of components of the TGF-xcex2 signaling system in neurons and may contribute to chronic neurodegenerative disease.
One of the most well characterized in vivo actions of TGF-xcex2 is its ability to mediate a wound-healing cascade, which results in accelerated tissue repair. At the site of a peripheral wound, degranulation of platelets releases a bolus of TGF-xcex2, which initiates a number of biological responses. Monocytes, lymphocytes, neutrophils and fibroblasts are recruited to the wound site as a result of chemotactic activity of TGF-xcex2. Autoinduction of TGF-xcex2 in a number of cell types maintains high levels of the growth factor in the wound bend, where it induces angiogenesis and production of extracellular matrix to aid in tissue repair.
TGF-xcex2 may have similar functions with regard to tissue repair in the central nervous system as it does in peripheral organs. Neuronal injury can result from a variety of insults, including physical trauma, hypoxia, excitotoxins, cytotoxins, reactive oxygen species, neurotrophic factor deprivation or infection. The expression of TGF-xcex2 often increases in areas of neuronal dysfunction.
Additionally, TGF-xcex2 maintains neuronal survival and reduces infarct size in a number of animal or mammal models of stroke. A local inflammatory response occurs as part of the wound healing process of the central nervous system, and then resolves as the damaged area is repaired. The TGF-xcex2 produced by glial cells disappears as the inflammatory response subsides. In these circumstances, it appears that TGF-xcex2 may be effective in reducing neuronal damage or providing neuroprotection against damage, e.g., by the amyloid plaques of Alzheimer""s diseases or excitatory insults.
The activation of metabotropic glutamate receptors (mGluR), which are selectively activated by N-acetylaspartylglutamate, in glial cultures has been reported to regulate the release of TGF-xcex2. Bruno et al., xe2x80x9cNeutralizing Antibodies for TGF-xcex22 Prevent Neuroprotection Mediated by Group-II Metabotropic Glutamate Receptors (mGluRs) in Cortical Culturesxe2x80x9d, Neurosci. Abs., 2299 (1997); and Wroblewska et al., xe2x80x9cN-Acetylaspartyglutamate Selectively Activates mGluR3 Receptors in Transfected Cellsxe2x80x9d, J. of Neurochemistry, 69:1, 174-81 (1997). Thus, only a few naturally-occurring compounds have been used to increase TGF-xcex2 activity.
However, synthetic and purity issues often arise whenever naturally derived materials, proteins, or other large molecules, are used in vivo. Accordingly, there remains a need for relatively small molecules to regulate the release of endogenous TGF-xcex2, both to produce more reliable effects and to simplify the synthesis of pharmaceutically useful compounds.
The present invention provides a method of treating a disease or condition in a mammal by administering an effective amount of a NAALADase inhibitor to said mammal in need of such treatment. The disease or condition may be selected from the group consisting of neurodegenerative disorders, cell-growth related diseases, infectious diseases, wound healing, immune related diseases, epithelial tissue scarring, collagen vascular diseases, fibroproliferative disorders, connective tissue disorders, inflammatory diseases, respiratory distress syndrome, and infertility.
In another embodiment, the disease or condition to be treated includes impaired immune function, extracellular matrix formation disorders, diabetes, autoimmune disorders, inflammatory diseases, cell-growth related disorders wherein the cells which are selected from the group consisting of kidney cells, hematopoietic cells, lymphocytes, epithelial cells, neuronal cells, and endothelial cells.
In yet another embodiment, the method includes treatment of a disease or condition that is evidenced by an abnormal level TGF-xcex2.